Core drills are widely used within the contracting industry in order to make holes in walls, roofs and/or floors. In case these consist of bricks, concrete or the like, water must be supplied during work. Normally this takes place via a channel in the drilling shaft. Conventionally, the water is led into the channel of the drilling shaft via the front part of the gear box housing. This has some considerable drawbacks; firstly, the drilling shaft is large in this part of the transmission, which means that the radial lip seals that are necessary in order to prevent water leakage must be made correspondingly large, which in turn makes the sealing more difficult and results in the seals getting worn out relatively quickly due to the high circumferential speed of the drilling shaft in the sealed portion, and secondly, extensive dismantling of large portions of the gear box, the drilling shaft and/or the gear box housing is often required when the seals are to be exchanged.
Also in connection with the changing of bearings or other repair or maintenance operations, extensive dismantling must be performed in case of prior art core drilling machines, e.g. involving the emptying of oil from the gear box housing. In practice, extensive dismantling of the front parts of the core drilling machine, comprising the gear box housing, may be required also when repair or maintenance operations are to be conducted on the motor housing.
GB 883684 as well as 125733 shows an example of a drilling machine that results in many of these problems in connection with dismantling and repair. Both of these have a single and common end cover between the motor housing and the gear box housing.